1. Field of the Invention
The present invention relates to a new compound for use as fuel oil additive and the method of preparing same for controlling the size of wax crystals formed in a low temperature fuel oil and preventing the cohesion of the wax crystals in a fuel oil, by using together with the wax crystal modifier and, more particularly, an amine salt or amide compound of following formula (I) prepared by reacting a pri-, sec- or tert-aliphatic amine containing alkyl group of 1-30 carbon atoms with 9,10-dihydroanthracene-9,10-endo-.alpha.,.beta.-succinic acid or an anhydride thereof: ##STR1## wherein, X is NR.sub.1 R.sub.2 or ONHR.sub.3 R.sub.4 R.sub.5 and Y is NR.sub.6 R.sub.7 or ONHR.sub.8 R.sub.9 R.sub.10 wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9 and R.sub.10 are hydrogen or straight chained alkyl group with 1-30 carbon atoms and they may be different or the same as each other, but all of them cannot be hydrogen.
2. Description of the Prior Art
Even a petroleum fraction with a high boiling point should be collected to obtain as much as possible of an amount of fuel oil from crude oil with moderate quality, containing large quantities of paraffin wax of high molecular weight by fractional distillation and thereby the paraffin wax of high molecular weight is increased in the fuel oil issuing from the process. The fuel oil has a feature in which the fluidity is decreased depending on the temperature decrease of the fuel oil, because the wax crystal extracted and grown in the fuel oil blocks a filter in a supply pipe and pipe arrangement in a diesel engine and thereby prevents the fuel oil from flowing.
There have been known many additives which act as wax crystal modifiers, added in wax-containing fuel oils to solve said problems. Said composition can modify the size and shape of the wax crystal and has the function of providing a fuel oil with fluidity even at a low temperature by improving the diffusion property of the wax crystal in a fuel oil.
Various pour point depressants, flow improvers, and fluidity improvers (hereinafter flow improvers) are disclosed in the literature and are commercially available. For instance, Korean Patent Publication No.91-4942 discloses a copolymer consisting of a vinyl ester of a carboxylic acid with a number average molecular weight of 1,000-6,000, containing 1-4 carbon atoms and ethylene, and 32-35 wt % of vinyl ester. British Patent No.1469016 shows the employment of a copolymer of di-n-alkyl fumarate and vinyl acetate as a co-additive, with ethylene-vinyl acetate copolymer to improve the low temperature fluidity of fuel oil with a high final boiling point. Polar compounds other than the copolymers aforementioned, which can suppress the growth of the wax crystal have been combined and used as ionic or non-ionic compounds. For example, U.S. Pat. No. 3,982,909 discloses that dicarboxylic acid or amine salt and/or amide of dicarboxylic monoester, obtained by reacting maleic anhydride with hydrogenated tallow amine is co-added together with flow improvers of ethylene structure, as an additive for middle distillate fuel oil. U.S. Pat. No.4,402,708 discloses amine salt and/or amide, a resultant of the reaction with phthalic acid or anhydride thereof and sec-aliphatic amine containing 16-40 carbon atoms.
The inventors accomplished the present invention, on the basis that nitrogen-containing polar compounds, other than the flow improvers mentioned in the above prior art, can be used with a polymer having an ethylene structure and/or a terpolymer of dialkyl fumarate-vinyl ester-vinyl ether to improve the fluidity of a fuel oil and a wax diffusion property in a fuel oil.